I think the only detail we've been given re the new skills and feeding is that they'll be more visceral.
My question is, will they still look like an extension of nightblade?
I've always regarded the existing abilities as nightblade plus. Visually being all black and red they're the best class fit and functionally, drain essence also fills a hole in the nightblade arsenal by providing a ranged (albeit only mid) non-finisher single target damage (not DOT) ability. Mist form plugs another hole - mega damage evasion.
From the other end, nightblade and sorcerer (courtesy of the daedric connection) have been the best class fit lore wise. Now necros too. But in terms of abilities you'd expect a vampire to have, nightblade with invisibility, life drains, healing using health as resource etc. still looks comfortably ahead. Definitely when taking into account visuals.